Isolines Isolines = lines that connect points of equal values. (iso = equal) The “values” can be anything… temp, pressure, elevation, etc.

Topo Map

Isolines

Isoline Rules 1.Isolines connect points of equal value. 2.Isolines are gentle, curving lines - no sharp corners.  15 55 55  10

Isoline Rules 3.Isolines are always closed curves, even though the map might only show part of it.

Isoline Rules 4.Isolines NEVER cross - this would mean that one point has two different values. 50 °60 ° XX YY ZZ 40 ° 30 ° 20°

Gradient Gradient = change in value / change in distance shows how quickly the value changes (rate). For topo maps: -- lines close together = steep slope. -- lines far apart = gentle slope.

Topographic Maps “Topo” maps use isolines (contour lines) to show elevation. Show 3D land on 2D surface. Show natural and man-made features. – Ex. lakes, rivers, roads, buildings, etc.

Topo Map

Rising Water

Contour Map

Contour Lines

Contour Interval = difference in elevation between two contour lines. Hachure Line = show depressions / holes The first depression line has same value as last regular contour line. ** Points between lines can be any value within interval range. Ex. point between 20’ and 30’ contour lines can be 21’ – 29’.

Contour Lines Contour lines that cross rivers/streams point upstream.